Apparatus for cleaning planar objects

ABSTRACT

RELATIVELY LIGHTWEIGHT OBJECTS SUCH AS ELECTRONIC CIRCUIT BOARDS MAY BE CLEANED BY ALLOWING THE OBJECT TO PASS BETWEEN PAIRS OF OPPOSED CYLINDRICAL DRIVE BRUSHES THAT ARE ROTATED AT A SPEED SUCH THAT THE OBJECT IS DRIVEN IN A PREDETERMINED DIRECTION AT A SPEED EQUAL TO THE TANGENTIAL VELOCITY OF AN OUTER EDGE PORTION OF EACH BRUSH. THE DRIVE BRUSH BRISTLES APPLY CLEANING FORCES SUBSTANTIALLY PERPENDICULAR TO THE SURFACE OF THE OBJECT. IN ADDITION, INDEPENDENTLY DRIVEN PAIRS OF OPPOSED CYLINDRICAL SKIMMING BRUSHES MAY BE PROVIDED BETWEEN CERTAIN PAIRS OF THE DRIVE BRUSHES ALONG THE PATH TRAVELED BY THE OBJECT, AND THE SKIMMING BRUSHES ARE ROTATED IN A DIRECTION TENDING TO AID THE MOVEMENT OF THE OBJECT ALONG THE PATH IN THE PREDETERMINED DIRECTION AND AT A SPEED SUCH THAT THE TANGENTIAL VELOCITY OF AN OUTER EDGE PORTION OF EACH SKIMMING BRUSH SUBSTANTIALLY EXCEEDS THE SPEED OF THE OBJECT, THEREBY APPLYING TANGENTIAL CLEANING FORCES. CLEANING OF THE OBJECT IS IMPROVED WHEN CARRIED OUT IN THE PRESENCE OF A CLEANING SOLVENT.

March 2, 1971 w. R. HAMILTON 3,556,429

APPARATUS FOR CLEANING PLAN'AR OBJECTS Filed June 20, 1968 3 Sheets-Sheet l Q N "3 Q M31 Q INVENTOR. W/LL/AM R. HAM/LTON fiM/WZ BY l'i iy- March 2, 1971 w, HAMILTON I 3,566,429

APPARATUS FOR CLEANING PLANAR OBJECTS Fiied June 20, 1968 3 Sheets-Sheet s IN l/E N 7' 0R.

W/LL/AM R HAM/U'O/V EH 1] I United States Patent 3,566,429 APPARATUS FOR CLEANING PLANAR OBJECTS William R. Hamilton, Western Springs, 11]., assignor to Baron Blakeslee, Inc., Chicago, Ill. Filed June 20, 1968, Ser. No. 738,576 Int. Cl. A46b 13/02 US. Cl. --77 14 Claims ABSTRACT OF THE DISCLOSURE Relatively lightweight objects such as electronic circuit boards may be cleaned by allowing the object to pass between pairs of opposed cylindrical drive brushes that are rotated at a speed such that the object is driven in a predetermined direction at a speed equal to the tangential velocity of an outer edge portion of each brush. The drive brush bristles apply cleaning forces substantially perpendicular to the surface of the object. In addition, independently driven pairs of opposed cylindrical skimming brushes may be provided between certain pairs of the drive brushes along the path traveled by the object, and the skimming brushes are rotated in a direction tending to aid the movement of the object along the path in the predetermined direction and at a speed such that the tangential velocity of an outer edge portion of each skimming brush substantially exceeds the speed of the object, thereby applying tangential cleaning forces. Cleaning of the object is improved when carried out in the presence of a cleaning solvent.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to cleaning devices, and more particularly relates to devices adapted to clean objects having substantially flat surfaces, such as electronic circuit boards and the like.

Description of the prior art A number .of devices adapted to clean relatively fiat objects have been developed in the past. For example, in US. Pat. No. 2,488,907, Griffin et al. describe a Washing unit used in the treatment of mounted animal skins in which cylindrical brushes are rapidly driven in a direction opposing the motion of the mounted skins through the machine. In US. Pat. No. 2,264,885, Mueller describes apparatus for the treatment of heavy gauge brass strips in which pairs of opposed wringer rollers pull the strips through the washing unit of the machine. In the washing unit, the strips are acted on by pairs of opposed cylindrical brushes that are rapidly rotated in a direction aiding the movement of the strips through the machine. Similarly, in US. Pat. No. 2,269,807, Buckley describes a machine used to scrub glass and porcelain plates in which pairs of opposed cylindrical brushes are driven at high speed in order to skim the surface of the plates and thereby propel them through the machine.

Although each of the above-discussed cleaning machines may be adequate for cleaning relatively heavy, fiat objects, such as boards, glass plates, and sheets of heavy gauge metal, each has exhibited deficiencies that have substantially limited its usefulness for cleaning relatively lightweight, thin, planar objects such as electronic circuit boards and the like. It has been found that in ice carrying out the methods for producing such circuit boards, as disclosed in Eisler U.S. Pats. Nos. Re. 24,165; 2,441,960; and 2,706,697, it is especially important that the coatings applied during the production process be quickly, yet reliably, removed.

SUMMARY OF THE INVENTION In contrast to prior art cleaning devices which generally employ rotatable brushes operated at velocities much faster than the speed of objects moved through the devices, it has been discovered that cleaning effectiveness and thoroughness can be surprisingly improved by revolving such brushes at a speed such that the tangential velocity of an outer edge portion of each brush would be substantially the same as the speed at which the object is moved past the brushes. If the speed of the brushes is regulated in the manner described, the bristles attached to each brush tend to remain in upright and radial positions as they come in contact with the object. As a result, the bristles exert a poking action on the object that is surprisingly effective in removing imbedded contamination and appears to be a method of cleaning completely lacking in and unappreciated by the prior art. When operated in the described manner, the bristles on each brush appear to apply cleaning forces along a direction that is substantially perpendicular to the flat surfaces of the object, thereby cleaning the object with remarkable efficiency and thoroughness.

In accordance with the present invention, a preferred device adapted to clean an object having a substantially flat surface would comprise cylindrical cleaning means having an outer edge portion adapted to apply cleaning forces to the object to be cleaned, and drive means for causing cylindrical cleaning means to move such that the outer edge portion thereof moves at a predetermined velocity, the cylindrical cleaning means being adapted to move the object to be cleaned along a path through the device substantially at the predetermined velocity and to apply generally perpendicular cleaning forces to the substantially flat surface of the object whereby the object is cleaned.

Contamination loosened by the cleaning means, together with additional surface foreign matter may be removed from the object by also employing additional cylindrical cleaning means, the outer edge portion of which is adapted to skim the flat surface of the object at a tangential speed substantially greater than the predetermined rate of speed, such that cleaning forces are applied to the object in a direction substantially tangential to the flat surface thereof.

An object of the present invention is to provide a device adapted to apply cleaning forces substantially perpendicular to the surface of an object being cleaned.

It is another related object of the present invention to provide a cleaning machine in which an object to be cleaned is moved through the machine primarily by contact with rotating cylindrical brushes.

It is yet another object of the present invention to provide a cleaning machine in which cylindrical brushes may be rotated at various speeds in order to apply cleaning forces both parallel and perpendicular to the surface of an object being cleaned.

Another object of the present invention is to provide an improved chain and sprocket drive means for a cleaning machine employing rotatable brushes.

Still another object of the present invention is to provide improved apparatus for sealing cleaning solvent 1nside a cleaning apparatus.

-DESCRIPTION OF THE DRAWINGS The foregoing objects, advantages, and features of the present invention will hereinafter appear, and, for purposes of illustration, but not of limitation, an exemplary embodiment of the apparatus aspect of the present invention is illustrated in the accompanying drawing, in which:

FIG. 1 is a partially schematic, fragmentary, top-plan view of a portion of a cleaning machine made in accordance with the present invention;

FIG. 2 is a partially schematic, fragmentary, front elevational view of the machine shown in FIG. 1;

FIG. 3 is a partially schematic, fragmentary, rear elevational view of the machine shown in FIG. 1;

FIG. 4 is an enlarged, cross-sectional, partially fragmentary view taken along line 4-4 in FIG. 1;

FIG. 5 is an enlarged, cross-sectional, partially fragmentary view taken along line 5-5 in FIG. 1;

FIG. 6 is an enlarged, cross-sectional, partially fragmentary view taken along line 66 in FIG. 1; and

FIG. 7 is an enlarged, partially fragmentary view taken along line 7-7 in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings, a preferred embodiment of a machine made in accordance with the apparatus aspect of the present invention would include in combination a frame 10, a drive brush assembly 40, a skimming brush assembly 170, a roller assembly 230, a rear drive assembly 270, a front drive assembly 400, and a cleaning fluid apparatus 460.

As best seen in FIGS. 1-3, frame 10 comprises a bot tom 11 and vertical side walls 12-15 that are adapted to hold various cleaning substances and to provide a firm foundation on which additional apparatus may be suspended. Although a variety of materials may be successfully employed, the vertical side walls and bottom are preferably made from stainless steel panels welded in place.

Frame 10 also comprises horizontal cross beams 18- 20 that are fastened between side walls 12 and 14. The cross beams are used to support a front beam 22 and a rear beam 24 between which drive brush assembly 40 and skimming brush assembly 170 are mounted. The front beam and rear beam are also held in place by top beams 26, 27 fastened between the respective end portions of the front and rear beams, and top beams 30-32 that are fastened directly above cross beams 18-20, respectively.

Frame 10 also comprises a feed shelf 34 attached to the top edge of side wall 15, and a discharge shelf 35 mounted to the top edge of side wall 13. A top (not shown) may be provided along the entire length of the frame in order to retain cleaning fluids and vapors inside the machine.

Drive brush assembly 40 comprises a plurality of drive brush pairs 44-61 that are rotatably mounted between front beam 22 and rear beam 24. As best seen in FIGS. 1 and 2, drive brush pairs 44-61 comprise a plurality of upper cylindrical drive brushes 66-83, respectively, and a like plurality of lower cylindrical drive brushes 106- 123, respectively. Upper drive brushes 66-83 are mounted on shafts 86-103, respectively, and lower drive brushes 106-123 are mounted on shafts 126-143, respectively.

Each of the drive brushes is identical, and the construction features of all can be understood from the detailed illustration of exemplary upper cylindrical drive brush 74 shown in FIG. 6. With reference to FIG. 6, brush 74 comprises bristles, generally denoted by the reference numeral 145, that are imbedded in a mounting drum 146. The mounting drum is fitted with an end disc 148 that, in turn, fits into a mounting collar 150 surrounding shaft 94. Shaft 94, in turn, is rotatably mounted in rear beam 24 through a bearing 152.

A variety of drive brushes may be used in connection with the present invention. However, when the invention is used to clean lightweight, substantially planar objects, such as electronic circuit boards, the brushes are preferably about 2 /2 inches in diameter and utilize bristles about 1% inches long. The bristles are preferably made from .008 inch diameter nylon. Of course, other abrasion and solvent resistant bristles may be used.

The manner in which the outer edge portions of the upper and lower cylindrical drive brushes in each pair co-act is best illustrated in FIGS. 5 and 6. As shown in FIG. 5, brush pair 50 comprises an upper cylindrical drive brush 72 and a lower cylindrical drive brush 112 that are vertically aligned so that an outer edge portion 158 of brush 72 overlaps slightly with an analogous outer edge portion 160 of brush 112. Likewise, as shown in FIG. 6, drive brush 74 has an outer edge portion 154 that co-mates with an outer edge portion 156 of drive brush 114. The bristles of each pair overlap slightly (i.e., about Ai-Mi inch) and hence are self-cleaning as will be described hereinafter in detail. The remaining drive brush pairs are arranged in an identical manner, and the exact placement of brushes within any pair can be readily understood with reference to the foregoing explana tion of the drive brush pairs shown in FIGS. 5 and 6.

Skimming brush assembly comprises a plurality skimming brush pairs 172-179 that include a plurality of upper cylindrical skimming brushes 182-189, respectively, and a like plurality lower cylindrical skimming brushes 202-209, respectively. Upper brushes 182-189 are mounted on shafts 192-199, respectively, and lower brushes 202-209 are mounted on shafts 212-219, respectively. Each of the shafts 192-199 and 212-219 are rotatably mounted between front beam 22 and rear beam 24, and, in addition, shaft 199 is rotatably mounted in vertical side wall 14.

Each of the skimming brushes is constructed in a manner identical to previously described upper cylindrical drive brush 74, the upper and lower skimming brushes in each pair are arranged in a manner identical to the arrangement of previously described drive brush pairs 50 and 51. Thus, as shown in FIG. 5, skimming brush pair is arranged so that an outer edge portion 222 of brush exactly meets with an analogous outer edge portion 224 of brush 205.

Roller assembly 230 comprises a pair of feed rollers 232, 233 mounted on a pair of shafts 236, 237, respectively, and a pair of discharge rollers 240, 241, mounted on a pair of shafts 244, 245, respectively. Each of the shafts 236, 237, and 244, 245 are rotatably mounted between front beam 22 and rear beam 24. In addition, shaft 245 is rotatably mounted, at its end points, in vertical side walls 12 and 14. Shaft 236 is mounted in a pair of slots 238, 239, and shaft 244 is mounted in a pair of slots 246, 247 in order to allow rollers 232 and 240, respectively, to float freely in a vertical direction.

Each of the rollers is made in an identical manner which may be understood with reference to exemplary roller 232 that is illustrated in detail in FIG. 4. As shown in FIG. 4, feed roller 232 is formed of resilient material 248 that is attached to a mounting drum 250. The mounting drum is fitted into an end disc 252 that, in turn, mates with a mounting collar 254 surrounding shaft 236. Shaft 236, in turn, is rotatably mounted in rear beam 24 through slot 239.

Rollers 232, 23-3 and 240, 241 are designed to retain cleaning fluids and vapors within the apparatus without impairing the passage of an object to be cleaned into the interior thereof. In order to achieve the foregoing goal, the resilient material 248 used in connection with roller 232 may be made from a variety of substances, but is preferably manufactured from a fiuorinated elastomer available from E. I. du Pont de Nemours & Co. under the trade mark Viton, a material which is preferred by reason of its inertness to the solvents used in the device and by reason of its toughness and resistance to wear.

As best seen in FIG. 4, the rollers are mounted above and below each other so that outer edge portion 232 of roller 232 exactly meets with outer edge portion 233 of roller 233. When the rollers are arranged as shown in FIG. 4, the feed end of the machine (i.e., the end adjacent feed shelf 34) is effectively sealed, and cleaning fluid and vapors are thereby retained in the machine. Nonetheless, since the material 248 is resilient and since roller 232 is mounted in slots that allow vertical movement, objects may pass betwen the rollers without difficulty.

Discharge rollers 240 and 241 are constructed and arranged in a manner identical to feed rollers 232, 233, respectively, and may be readily understood with reference to the foregoing description of the rollers illustrated in FIG. 4.

Rear drive assembly 270 includes sprockets 272 and 274 connected to discharge roller 241 and feed roller 233 through shafts 245 and 237, respectively. Sprockets 272 and 274 are identical and can be readily understood from the detailed illustration of sprocket 274 in FIG. 4. With reference to FIG. 4, sprocket 274 comprises a sprocket cylinder 275 that is integrally formed with two sets of sprocket teeth 276 and 277, and is rigidly attached to shaft 237 by a key pin 278. Preferably sprockets 272 and 274 are made from a rigid substance suitable for use in connection with a chain drive. It has been found that a Browning No. D-40-B-14, 14 tooth sprocket is suitable for such purposes.

Rear drive assembly 270 also comprises a plurality upper sprockets 280-297 that are connected to the shafts on which upper cylindrical drive brushes 66-83 are mounted, and a plurality lower sprockets 300-317 that are conected to the shafts on which lower cylindrical drive brushes 106-123 are mounted. Each of the upper and lower sprockets is identical and can be understood with reference to sprockets 288 and 308 shown in FIG. 6. With reference to FIG. 6, sprocket 288 comprises a sprocket cylinder 328 that has an inner edge 330 and an outer edge 332. Sprocket teeth generally denoted by the number 334 are integrally formed with the sprocket cylinder and are located adjacent the outer edge thereof.

Sprocket 308 comprises a sprocket cylinder 336 and has an inner edge 338 and an outer edge 340. Sprocket teeth generally denoted by the reference numeral 342 are integrally molded with the sprocket cylinder and are arranged adjacent the inner edge thereof. The arrangement of teeth on the inner and outer edges of sprockets 308 and 288, respectively, enables sprockets 308 and 288 to overlap to some extent. That is the teeth on sprocket 288 are arranged to extend into a plane lower than the upper plane into which the teeth on sprocket 308 extend. Thus, the arrangement shown in FIG. 6 allows sprockets of a given size to be arranged in a minimum amount of space. Sprockets 288 and 308 are rigidly attached to shafts 94 and 134 by key pins 335 and 344, respectively.

The sprockets attached to drive brush pairs 44, 46, 48, 50, 54, 56, 58, and 60 are fabricated and arranged in a manner identical to the sprockets attached to drive brush pair 52 (i.e., sprockets 288 and 308 illustrated in FIG. 6) and may be understood with reference thereto.

The sprockets connected to drive brush pairs 45, 47, 49, 51, 53, 55, 57, 59, and 61 are identical to the type of sprockets shown in FIG. 6, except that the upper and lower sprockets in each pair are reversed; that is, a sprocket having its teeth located adjacent the inner edge of its sprocket cylinder is used in connection with the upper drive brush and a sprocket having its teeth located adjacent the outer edge of its sprocket cylinder is used in connection with the lower drive brush in each of the aforementioned odd-numbered pairs. A pair of sprockets 281,

6 301 arranged according to the foregoing description is illustrated in FIG. 7, and all additional sprocket pairs arranged in a like manner may be readily understood with reference thereto.

Rear drive assembly 270 also comprises an electric motor 350. Although the optimum size of the motor will vary depending upon the particular application involved, it has been found that a half-horsepower, 2400 r.p.m. motor is generally suitable when the machine is used to clean relatively lightweight, substantially planar objects. As best seen in FIG. 1, the output of motor 350 is applied through a speed reducer 352 and a torque limiter 354 to shaft 245 that is, in turn, connected to discharge sealing roller 241. Although a variety of speed reducers and torque limiters may be successfully employed, a Grant :1, 225-DBF, speed reducer and a Morse No. 350-1 torque limiter are especially adapted for use in connection with the present invention.

As best seen in FIGS. 1 and 3, the power of motor 350 is transmitted to each of the sprockets in the rear drive assembly through a double roller chain 360. With reference to FIGS. 4 and 6, double roller chain 360 comprises an inner chain 362 and an outer chain 364 that share a common set of center links 366. In addition, chain 360 comprises cross bars, generally denoted by the number 368, associated with inner chain 362, and cross bars, generally denoted by the number 369, associated with outer chain 364. As shown in FIGS. 4 and 6, the cross bars are adapted to co-act with the teeth of the various sprockets in order to transmit power from motor 350 to each of the drive brushes associated with the respective sprockets.

As best seen in FIG. 3, chain 360 is oriented between the upper and lower sprockets associated with each pair of drive brushes, and is also looped around sprockets 272 and 274 associated with the lower sealing rollers. In addition, chain 360 is looped around sprocket 372 that is held to cross beam 19 by brackets 3-74 and 376. Sprocket 372 is adjustable through brackets 374, 376 in order to provide a proper degree of tension on chain 360.

As best seen in FIGS. 1 and 2, front drive assembly 400 comprises a sprocket 402 that is used to drive skimming brush 209, and an idler sprocket 404 that is used to support the end of a chain drive mechanism as described hereafter. Front drive assembly 400 also com prises upper sprockets 406-412 that are used to drive upper skimming brushes 182-188, respectively, and lower sprockets 416-422 that are used to drive lower skimming brushes 202-208, respectively. Sprocket pairs 406, 416; 408, 418; 410, 420; and 412, 422 are fabricated and arranged in a manner identical to sprocket pairs 28 8, 308 illustrated in FIG. 6, and may be readily understood from the description thereof. Sprocket pairs 407, 417; 409, 419; and 411, '421 are fabricated in an identical fashion, but have their respective teeth oriented in a manner reversed from the arrangement shown in connection with sprockets 288, 208 in FIG. 6 (i.e., in a manner like the arrangement of sprockets 2'81, 301, shown in FIG. 7); that is, upper sprockets 407, 409, and 411 have their teeth arranged adjacent the inner edge of their sprocket cylinders, and lower sprockets 417, 419, and 421 have their teeth arranged adjacent the outer edge of their sprocket cylinders. The foregoing arrangements may be achieved by simply reversing the position of the sprockets on their respective shafts from the positions shown in FIG. 6.

Front drive assembly 400 also comprises an electric motor 430. Although a variety of electric motors may be successfully used, it has been found that a one-third horsepower, 2400 r.p.m. motor is most suitable for cleaning relatively lightweight, fiat objects. As best shown in FIG. 1, motor 430 is connected through a speed reducer 432 and a torque limiter 434 to shaft 219. A variety of speed reducers and torque limiters may be used in connection with the present invention, but it has been found 7 'that a Grant 20:1 175-STE speed reducer and a Morse No. 350-1 torque limiter are especially suitable.

As best seen in FIG. 2, front drive assembly 400 also comprises a double roller chain 440 that includes an inner chain, an outer chain, and common center links joining the inner and outer chains in a juxtaposition relationship. Chain 440 is made in a manner identical to double roller chain 360 and may be understood from the description thereof together with the illustrations of chain 360 in FIGS. 4, 6 and 7. Referring to FIG. 2, chain 440 is arranged between the upper and lower sprockets in sprocket pairs 406, 416; 407, 417; 408, 418; 409, 419; 410, 420; 411, 421; and 412, 422. In addition, the chain is looped around sprocket 402 that is used to drive lower skimming brush 209, and around idler sprocket 404 that is free to rotate on shaft 237. Moreover, chain 440 is arranged to co-act with sprocket 452 mounted on brackets 456, 458, that are, in turn, movably mounted on cross beam 19. Sprocket 452 is used to apply a proper degree of tension to chain 440.

Cleaning solvent apparatus 460 may comprise a variety of conventional devices suitable for handling solvents in automatic cleaning machines. Since such apparatus is well-known to those skilled in the cleaning arts it will only be described generally herein.

In general, cleaning solvent apparatus 460 comprises a feed end fixture 462 that is arranged adjacent feed shelf 34 andconnected to a duct 464, and a discharge end fixture 468 that is connected adjacent discharge shelf 35 and connected to a duct 470. Ducts 464 and 470 are, in turn, connected to a motordriven blower that is used to remove any cleaning solvent vapors that may enter the vapor fixtures from either the feed or discharge ends of the machine.

Cleaning solvent apparatus 460 also comprises a series of reservoirs (not shown) located inside vertical side walls 12-15. 'Pumps are used to transport cleaning fluids from the reservoirs to upper spray pipes 474-477 and lower spray pipes 480-483. Solvent is sprayed through nozzles in the pipes into the path of an object being cleaned, and excess fluid runs off the object and drips into certain of the reservoirs. Continual reconditioning of the solvent can be accomplished by use of a solvent recovery still installed either alongside the machine or at a remote location. Clean, reconditioned solvent from the recovery still is returned to the reservoir at the discharge end of the machine, from where the solvent cascades to the reservoir adjacent the feed end of the machine. The used cleaning solvent is then returned to the recovery still where the reconditioning cycle is repeated. Separate pumps and filters may be utilized in connection with each reservoir in order to minimize solvent contaminaiton.

Other analogous systems for handling cleaning solvent may of course be used in connection with the present invention, and the details of construction of such apparatus will be obvious to those skilled in the art.

In carrying out the method of the present invention, substantially any of the well known cleaning solvents may be employed. It is especially preferred that the inert halogenated hydrocarbon class of solvents such as CCl CHCl CH Cl C F Cl and the like be employed.

Operation of the machine in accordance with the method aspect of the present invention will now be described in detail. As best seen in FIGS. 1 and 2, an object to be cleaned 500, including an upper surface 502 and a lower surface 504, is placed near feed shelf 34. Although a variety of objects may be cleaned by the apparatus described herein, the present invention is especially adapted to clean relatively lightweight, flat, substantially planar objects, such as electronic circuit boards, varying in thickness from about 0.20 inch to about 0.250 inch, and in width from about 4 inches to the length of the brushes. The length of such objects may be from about 6 inches to substantially any greater length.

In order to operate the upper and lower cylindrical drive brushes, motor 350 is energized in order to move double roller chain 360 in the direction indicated by arrow A in FIG. 3. When the chain is driven as described, the upper cylindrical drive brushes are rotated in a clockwise direction (as viewed in FIG. 2), and the lower cylindrical drive brushes are rotated in a counterclockwise direction (as viewed in FIG. 2) so that object 500 is moved through the machine from feed shelf 34 to discharge shelf 35. When objects such as electronic circuit boards are to be cleaned, the objects are preferably propelled through the machine at a speed of from about 2 to 14 feet per minute, with the optimum speed being 7 feet per minute. In order to move the objects at the optimum speed, the speed of motor 350 is adjusted so that the tangential velocity of the outer edge portion of each cylindrical drive brush equals the optimum speed.

As best seen in FIGS. 1 and 3, chain 360 is also looped around sprockets 272 and 274 so that rollers 241 and 23 3, respectively, are revolved in the same direction and at the same speed as the lower cylindrical drive brushes.

The upper and lower cylindrical skimming brushes are operated by energizing motor 430 so that chain 440 is driven in the direction indicated by arrow B in FIG. 2. When chain 440 is driven as described, the upper cylindrical skimming brushes are driven in the same direction as the upper cylindrical drive brushes (i.e. clockwise as seen in FIG. 2), and likewise, the lower cylindrical skimming brushes are driven in the same direction as the lower cylindrical drive brushes (i.e., counter-clockwise as seen in FIG. 2).

The speed of motor 430 is regulated so that the upper and lower skimming brushes are rotated at a rate approximately 5 to 10 times the rate at which the upper and lower drive brushes are rotated; that is, the speed of motor 430 is regulated so that the tangential velocity of the outer edge portion of each skimming brush is approximately 5 to 10 times the optimum speed of object 500.

After the drive and skimming brushes are moving in the manner indicated, the cleaning fluid apparatus 460 is energized in order to pump cleaning fluid from the reservoirs between side walls 12-15 into the upper spray pipes 474-477 and lower spray pipes 480-483 so that a supply of fresh cleaning fluid is sprayed into the path traversed by object 500.

Object 500 is then manually moved onto feed shelf 34 and between feed rollers 232 and 233. Alternatively, the object may be transported to the shelf 34 by power driven conveyor means. Since roller 232 is mounted in slots 238, 239, it is readily movable in an upward direction in order to allow object 500 to pass between it and roller 233. Since roller 233 is driven at a relatively slow rate of speed and since object 500 is relatively lightweight, the object is rapidly accelerated to a rate equal to the tangential velocity of the outer edge portion of roller 233 (i.e., to the optimum speed). However, because upper roller 232 is free floating, the danger of damage to the object due to roller pressure is minimized, thereby avoiding the problems posed by the prior art drive rollers. If the object has not attained the optimum speed after passing over roller 233, it is quickly accelerated thereto as it passes between skimming brushes 182 and 202 adjacent the feed rollers. Thus, by the time object 500 reaches the initial drive brush pair 44 (FIG. 1), it has at least substantially attained the speed of the outer edge portions of the drive brushes, and thereafter continues to travel through the machine at approximately that speed.

Cleaning forces are applied to the upper and lower surfaces of object 500 as it passes between the upper and lower brushes of the various drive brush and skimming brush pairs. The manner in which the cleaning forces are applied to the object is best illustrated in connection with FIG. 5, where object 500 is shown moving past drive brush pairs 50, 51 and skimming brush pair in the direction indicated by arrow C. As previously explained, the speed of motor 350 is adjusted so that the tangential velocity of the outer edge portion of each of the drive brushes equals the optimum speed. For example, with reference to FIG. 5, the tangential velocities of the outer edge portion 158 of brush 72 and outer edge portion 160 of brush 112 equal the optimum speed at which the ob ject moves past the brushes. When the object moves between brushes 72 and 112 at substantially the optimum speed, the bristles in contact with the object tend to remain in essentially upright, radial positions, and as a result, tend to apply cleaning forces that are substantially perpendicular to the upper and lower surfaces of the ob ject. Moreover, since the bristles in contact with the object tend to remain relatively perpendicular with respect to the upper and lower surfaces thereof, they appear to exert a kind of poking action on the surfaces of the object that is surprisingly effective for removing imbedded dirt and contamination. This cleaning action has been found to be especially useful in cleaning the punched holes that are commonly found in electronic circuit boards. The remaining pairs of drive brushes act in an analogous manner as the object passes along the path arrow 510 (FIG. between the upper and lower brushes in each pair.

Additional cleaning forces designed to loosen surface contamination on object 500 are provided by the skimming brush pairs used in the machine. As previously explained, each of the upper and lower cylindrical skimming brushes is driven in a direction tending to aid the motion of object 500 along path 510 (i.e., the same direction as the upper and lower cylindrical drive brushes, respectively). Moreover, the skimming brushes are rotated at a speed such that the tangential velocity of the outer edge portion of each brush substantially exceeds the rate at which the object moves along the path. That is, the tangential velocity of the outer edge portion of each skimming brush substantially exceeds the tangential velocity of the outer edge portion of each drive brush.

When the skimming brushes are driven in the manner described, the bristles attached thereto are flexed as they rapidly turn past object 500, so that the bristles primarily apply cleaning forces in a direction substantially tangential to the upper and lower surfaces of the object. Such cleaning forces tend to loosen surface contamination, and when used in combination with the perpendicular cleaning forces produced by the drive brushes, provide an effective means for rapidly and thoroughly cleaning a flat object.

Although the skimming brushes are driven at a much faster rate than the drive brushes, they do not tend to significantly increase the speed of object 500 above the speed of the drive brushes because of the relative numbers of drive and skimming brush pairs. Indeed, as a practical matter, the object usually moves through the unit at an actual speed that is somewhat less than the optimum predetermined speed (most commonly at a speed of the order of magnitude of about 90% of the tangential velocity of the outer edge tips of the drive brush bristles), and as used herein the term substantially at the predetermined speed is intended to encompass such actual speeds.

After the object has passed between the upper and lower brushes in each pair of drive and skimming brushes, it passes between discharge rollers 240, 241 and is moved onto discharge shelf 35. Thereafter, the object may be conveyed away from the machine, either manually or automatically, and the cleaning fluid is allowed or caused to evaporate from the surfaces of the object.

As previously mentioned, the pairs of drive and skimming brushes are interfering (i.e., overlap slightly) and thus the brushes are self-cleaning when they are not acting on flat objects. This interference further contributes to the effectiveness of the subject invention in cleaning holes and cavities in planar objects.

When the described apparatus is used according to the methods taught herein, the upper and lower surfaces of an object can be treated by cleaning forces oriented both 10 perpendicular and tangential to the surfaces thereof. Such techniques result in a thorough cleaning action that has a degree of efficiency and thoroughness unattained and unappreciated by prior art devices and methods, and yet without risk of damage to the machine.

I claim: 1. A device adapted to clean objects having substantially fiat surfaces comprising:

cylindrical cleaning means having an outer edge portion adapted to apply cleaning forces to an object to be cleaned, said cleaning means having radially extending cleaning elements thereon; drive means for causing the cylindrical cleaning means to move such that the outer edge portion thereof moves at a predetermined velocity, the cylindrical cleaning means being adapted to move the object to be cleaned along a path through the device substantially at the predetermined velocity and to apply generally perpendicular cleaning forces to the substantially fiat surface of the object whereby the object is cleaned. 2. A device adapted to clean objects having substantially fiat surfaces comprising:

cylindrical cleaning means having an outer edge portion adapted to apply cleaning forces to an object to be cleaned, the cylindrical cleaning means comprising at least one pair of opposed, rotatably driven cylindrical brushes disposed, respectively, on opposite sides of the path through which the object moves; and drive means for causing the cylindrical cleaning means to move such that the outer edge portion thereof moves at a predetermined velocity, the cylindrical cleaning means being adapted to move the object to be cleaned along a path through the device substantially at the predetermined velocity and to apply generally perpendicular cleaning forces to the substantially flat surfaces of the object, whereby the object is cleaned. 3. A device, as claimed in claim 2, wherein the outer edge portions of the brushes of each pair normally are in interference with each other.

4. A device, as claimed in claim 2, wherein the drive means comprises:

first sprocket means having a plurality of teeth thereon,

the said first sprocket means being operatively connected to a first cylindrical brush of said pair; second sprocket means having a plurality of teeth thereon, the said second sprocket means being operatively connected to a second cylindrical brush of said pair, the teeth on the first sprocket means and the teeth on the second sprocket means being arranged in different, but parallel and adjacent, vertical planes; motor means; and chain means including:

a first series of chain links adapted to mate with the teeth on the first sprocket means; a second series of chain links adapted to mate with the teeth on the second sprocket means; and means fixedly interconnecting the first and second series of chain links in side-by-side relationship, the chain means being operatively connected to the motor means and arranged between the first and second sprocket means, whereby the first and second cylindrical brushes of said pair are simultaneously driven in opposite directions. 5. A device, as claimed in claim 1, and further comprising:

second cylindrical cleaning means having an outer edge portion adapted to ap ly cleaning forces to the object to be cleaned, said cleaning means having radially extending cleaning elements thereon; and

second drive means for causing the second cylindrical cleaning means to move such that the outer edge portion thereof moves at a velocity in excess of the predetermined velocity,

whereby additional cleaning forces are exerted on the substantially flat surface of the object generally tangentially thereto.

6. A device adapted to clean objects having substantially fiat surfaces comprising:

first cylindrical cleaning means having an outer edge portion adapted to apply cleaning forces to an object to be cleaned;

first drive means for causing the cylindrical cleaning means to move such that the outer edge portion thereof moves at a predetermined velocity;

second cylindrical cleaning means having an outer edge portion adapted to apply cleaning forces to the object to be cleaned, the second cylindrical cleaning means comprising at least one pair of opposed, rotatably driven cylindrical brushes disposed, respectively, on opposite sides of the path through which the object moves; and

second drive means for causing the second cylindrical cleaning means to move such that the outer edge portion thereof moves at a velocity in excess of the predetermined velocity, the first cylindrical cleaning means being adapted to move the object to be cleaned along a path through the device substantially at the predetermined velocity and to apply generally perpendicular cleaning forces to the substantially flat surface of the object, and the second cylindrical cleaning means being adapted to exert additional cleaning forces on the substantially fiat surface of the object generally tangentially thereto, whereby the object is cleaned. 7. A device, as claimed in claim 6, wherein the outer edge portions of the brushes of each pair normally are in interference with each other.

8. A device, as claimed in claim 6, wherein the second drive means comprises:

first sprocket means having a plurality of teeth thereon,

the said first sprocket means being operatively connected to a first cylindrical brush of said pair;

second sprocket means having a plurality of teeth thereon, the said second sprocket means being operatively connected to a second cylindrical brush of said pair;

the teeth on the first sprocket means and the teeth on the second sprocket means being arranged in different, but parallel and adjacent, vertical planes; motor means; and

chain means including:

a first series of chain links adapted to mate with the teeth on the first sprocket means;

12 a second series of chain links adapted to mate with the teeth on the second sprocket means; and means fixedly interconnecting the first and second series of chain links in side-by-side relationship, the chain means being operatively connected to the motor means and arranged between the first and second sprocket means,

whereby the first and second cylindrical brushes of said pair are simultaneously driven in opposite directions.

9. A device, as claimed in claim 5, wherein the firstmentioned cylindrical cleaning means comprise a plurality of pairs of opposed, rotatably driven cylindrical brushes disposed on opposite sides of the path through which the object moves and the second cylindrical cleaning means comprise a plurality of pairs of opposed rotatably driven cylindrical brushes disposed on opposite sides of the path through which the object moves, the pairs of brushes of the second cylindrical cleaning means being substantially fewer in number than said pairs of brushes of the first-mentioned cylindrical cleaning means.

10. A device, as claimed in claim 1, and further comprising means for supplying a cleaning solvent to the region surrounding the cylindrical cleaning means thereby to supplement the cleaning action thereof.

11. A device, as claimed in claim 10, and further comprising feeding means for delivering the object to the cylindrical cleaning means at a velocity approaching the predetermined velocity.

12. A device, as claimed in claim 11, wherein the feeding means comprise a pair of opposed, resilient feeding rollers disposed on opposite sides of the path through which the object moves, the said feeding rollers being further adapted to sealingly retain cleaning solvent in the device.

13. A device, as claimed in claim 10, and further comprising discharge means for effecting removal of the object from the cylindrical cleaning means.

14. A device, as claimed in claim 13, wherein the discharge means comprises a pair of opposed resilient discharge rollers disposed on opposite sides of the path through which the object moves, the said discharge rollers being further adapted to sealingly retain cleaning solvent in the device.

References Cited V UNITED STATES PATENTS 2,293,858 8/1942 Schafer 1577 2,313,606 3/1943 Webb et al. 1577 2,385,511 9/1945 Hayes et a1 1577X EDWARD L. ROBERTS, Primary Examiner 

